This project is a study of radiation damage in nucleic acid constituents using a variety of experimental approaches including ESR, ENDOR and 13C NMR spectroscopy; also HPLC and mass spectrometry. Attention will be given to radiation effects in the carbohydrate and phosphate moieties of nucleic acids. Also of interest are the mediative effects of halogen substituted bases on the overall radiation damage process. For example cocrystals of 5 bromouridine and adenosine, X irradiated at 4.20K, are being studied by ESR-ENDOR spectroscopy to determine how halogenation alters the primary radiation damage process.